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Add pathfinding loop detection based on peep->pathfind_history 

The heuristic search currently only inludes detection of loops in the current search path - i.e. from where the peep is now.

The peep->pathfind_history includes (limited) junctions that the peep has already passed through for the current search goal to get to their current location. Consider search paths through these junctions as loops as well.

This will prevent peeps getting stuck in some path layouts where looping back through a junction they already walked through and then proceeding via an alternative path (such that there is no loop in the current search path) hits the search limits on a continuing path that is closer to the goal than simply continuing on along the path which then turns (temporarily) away from the goal.

This prevents _some_ cases of alternate, longer routes to nearer tiles being returned as a better result than a route that goes through that same tile (with less steps) and then continues on to end overall further from the goal though closer to getting to the goal (as was previously documented in PR #4527).

The network version is incremented in this PR.
This commit is contained in:
zaxcav 2016-10-23 18:55:47 +02:00
parent 88ccfad303
commit 86ae14c65d
2 changed files with 36 additions and 16 deletions
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2
src/network/network.h
View File

@ -55,7 +55,7 @@ extern "C" {
// This define specifies which version of network stream current build uses.
// It is used for making sure only compatible builds get connected, even within
// single OpenRCT2 version.
#define NETWORK_STREAM_VERSION "16"
#define NETWORK_STREAM_VERSION "17"
#define NETWORK_STREAM_ID OPENRCT2_VERSION "-" NETWORK_STREAM_VERSION
#ifdef __cplusplus

50
src/peep/peep.c
View File

@ -8974,7 +8974,7 @@ static bool path_is_thin_junction(rct_map_element *path, sint16 x, sint16 y, uin
*
* rct2: 0x0069A997
*/
static void peep_pathfind_heuristic_search(sint16 x, sint16 y, uint8 z, rct_map_element *currentMapElement, uint8 counter, uint16 *endScore, int test_edge, uint8 *endJunctions, rct_xyz8 junctionList[16], uint8 directionList[16], rct_xyz8 *endXYZ, uint8 *endSteps) {
static void peep_pathfind_heuristic_search(sint16 x, sint16 y, uint8 z, rct_peep *peep, rct_map_element *currentMapElement, uint8 counter, uint16 *endScore, int test_edge, uint8 *endJunctions, rct_xyz8 junctionList[16], uint8 directionList[16], rct_xyz8 *endXYZ, uint8 *endSteps) {
uint8 searchResult = PATH_SEARCH_FAILED;
x += TileDirectionDelta[test_edge].x;
@ -9280,21 +9280,41 @@ static void peep_pathfind_heuristic_search(sint16 x, sint16 y, uint8 z, rct_map_
* junction on this map element. Only 'thin' junctions
* are counted towards the junction search limit. */
/* Check the pathfind_history to see if this junction has been
* previously passed through in the current search path.
* i.e. this is a loop in the current search path.
* If so, the current search path ends here.
* Continue to the next map element without updating the parameters (best result so far). */
/* First check if going through the junction would be
* a loop. If so, the current search path ends here.
* Path finding loop detection can take advantage of both the
* peep->pathfind_history - loops through remembered junctions
* the peep has already passed through getting to its
* current position while on the way to its current goal;
* _peepPathFindHistory - loops in the current search path. */
bool pathLoop = false;
for (int junctionNum = _peepPathFindNumJunctions + 1; junctionNum <= _peepPathFindMaxJunctions; junctionNum++) {
if ((_peepPathFindHistory[junctionNum].location.x == (uint8)(x >> 5)) &&
(_peepPathFindHistory[junctionNum].location.y == (uint8)(y >> 5)) &&
(_peepPathFindHistory[junctionNum].location.z == (uint8)z)) {
pathLoop = true;
break;
/* Check the peep->pathfind_history to see if this junction has
* already been visited by the peep while heading for this goal. */
for (int i = 0; i < 4; ++i) {
if (peep->pathfind_history[i].x == x >> 5 &&
peep->pathfind_history[i].y == y >> 5 &&
peep->pathfind_history[i].z == z) {
pathLoop = true;
break;
}
}
if (!pathLoop) {
/* Check the _peepPathFindHistory to see if this junction has been
* previously passed through in the current search path.
* i.e. this is a loop in the current search path. */
for (int junctionNum = _peepPathFindNumJunctions + 1; junctionNum <= _peepPathFindMaxJunctions; junctionNum++) {
if ((_peepPathFindHistory[junctionNum].location.x == (uint8)(x >> 5)) &&
(_peepPathFindHistory[junctionNum].location.y == (uint8)(y >> 5)) &&
(_peepPathFindHistory[junctionNum].location.z == (uint8)z)) {
pathLoop = true;
break;
}
}
}
if (pathLoop) {
/* Loop detected. The current search path ends here.
* Continue to the next map element without updating the parameters (best result so far). */
#if defined(DEBUG_LEVEL_2) && DEBUG_LEVEL_2
if (gPathFindDebug) {
log_info("[%03d] Search path ends at %d,%d,%d; Loop", counter, x >> 5, y >> 5, z);
@ -9376,7 +9396,7 @@ static void peep_pathfind_heuristic_search(sint16 x, sint16 y, uint8 z, rct_map_
_peepPathFindHistory[_peepPathFindNumJunctions + 1].direction = test_edge;
}
peep_pathfind_heuristic_search(x, y, height, mapElement, counter, endScore, test_edge, endJunctions, junctionList, directionList, endXYZ, endSteps);
peep_pathfind_heuristic_search(x, y, height, peep, mapElement, counter, endScore, test_edge, endJunctions, junctionList, directionList, endXYZ, endSteps);
_peepPathFindNumJunctions = savedNumJunctions;
#if defined(DEBUG_LEVEL_2) && DEBUG_LEVEL_2
@ -9480,7 +9500,7 @@ int peep_pathfind_choose_direction(sint16 x, sint16 y, uint8 z, rct_peep *peep)
edges = peep->pathfind_history[i].direction & 0xF;
#if defined(DEBUG_LEVEL_1) && DEBUG_LEVEL_1
if (gPathFindDebug) {
log_verbose("Getting untried edges from pf_history for %d,%d,%d: %d", x >> 5, y >> 5, z, edges);
log_verbose("Getting untried edges from pf_history for %d,%d,%d: %s,%s,%s,%s", x >> 5, y >> 5, z, (edges & 1) ? "0" : "-", (edges & 2) ? "1" : "-", (edges & 4) ? "2" : "-", (edges & 8) ? "3" : "-");
}
#endif // defined(DEBUG_LEVEL_1) && DEBUG_LEVEL_1
break;
@ -9566,7 +9586,7 @@ int peep_pathfind_choose_direction(sint16 x, sint16 y, uint8 z, rct_peep *peep)
rct_xyz8 endJunctionList[16] = { 0 };
uint8 endDirectionList[16] = { 0 };
peep_pathfind_heuristic_search(x, y, height, dest_map_element, 0, &score, test_edge, &endJunctions, endJunctionList, endDirectionList, &endXYZ, &endSteps);
peep_pathfind_heuristic_search(x, y, height, peep, dest_map_element, 0, &score, test_edge, &endJunctions, endJunctionList, endDirectionList, &endXYZ, &endSteps);
#if defined(DEBUG_LEVEL_1) && DEBUG_LEVEL_1
if (gPathFindDebug) {
log_verbose("Pathfind test edge: %d score: %d steps: %d end: %d,%d,%d junctions: %d", test_edge, score, endSteps, endXYZ.x, endXYZ.y, endXYZ.z, endJunctions);